diff --git a/day13/day13.py b/day13/day13.py
index de59fb8..1e568bb 100644
--- a/day13/day13.py
+++ b/day13/day13.py
@@ -56,7 +56,7 @@ def score(self, row_reflect: Optional[int], col_reflect: Optional[int]) -> int:
             return col_reflect
         if row_reflect is not None:
             return 100 * row_reflect
-        raise ValueError("expected a mirror!")
+        raise AssertionError("expected a mirror!")
 
 
 def read_input(path: str) -> list[Maze]: